This invention relates to vertical form, fill and seal machines, and more particularly to a method and apparatus for gripping a bag and then processing the gripped bag downstream, such as applying a header label to the bag, particularly but not limited to after the bag has been filled by a vertical form, fill and seal machine.
When bags are formed by a vertical form, fill and seal machine, the bags are filled with a product and ready for further handling, such as packaging in a carton or downstream processing. If downstream processing is desired by a machine, it is important that the bag leave the vertical form, fill and seal machine under control, that is, held in proper alignment for its downstream processing. However, since the vertical form, fill and seal machine is also continuously forming bags in series, formed bags must also be moved out of the path of an oncoming bag as that bag is being formed in order to not interfere with the bag and therefore slow the operating speed of the vertical form, fill and seal machine.
For many years, labels, typically pre-printed paper labels, have been applied to the top of bags, originally as an inexpensive way of identifying the manufacturer and the contents of the bag, without having to print on the bag itself. This system used to be particularly important to manufacturers who had many different products, many of which could be packaged in the same size bag.
The cost of having printed bags for each different product was prohibitive, but it was relatively inexpensive to buy plain, unprinted bags and have small quantities of labels separately printed for various products. The labels, either being plain or heat seal coated, and the cost of sheet printing and cutting to size for the labels are relatively modest in relation to printing of different bags for different products.
The first machines for applying labels to bags were developed in the 1950's. These machines where semiautomatic, using clamping jaws to apply plain paper labels to bags. The operator typically placed the bag in a position adjacent to sealing jaws with a label in position, a folder blade folded the top of the bag and the label together, and the heated jaws were then closed on the bag under very high pressure. The combination of heat and pressure adhered the label to the bag top. Such machines were manufactured by the Doboy Company of New Richmond, Wis., U.S.A.
The rate of operation of these semiautomatic machines relied to a large degree on the dexterity of the machine operator. Rates of 20 to 25 bags per minute per operator are common, but given the required human interaction and stepwise functioning of the machine, much faster rates could not be obtained.
In order to increase productivity, continuous automatic machines where introduced in the late 1950's, also by Doboy Company. These machines operated at a rate of about 60 bags per minute, but because of their continuous motion, insufficient pressure could be generated to handle plain paper labels, and consequently more expensive heat seal coated label paper had to be used. An operator was still required to place the bag into the continuous motion infeed of the automatic machines. No means was provided for automatically gripping the bag and then introducing it into the continuously-moving machine.
Both semiautomatic and automatic machines, such as those described above, applied what is known in the industry as a "saddle label", a label that is folded so that a portion appears on both the front and rear of the bag. A saddle label can have equal portions on both the front and rear of the bag, or can be offset, usually to the front of the bag, so that a larger portion of the label appears on the bag front.
The Doboy machines also had the capability of punching a hole in the finished bag to enable the bag to pegged or racked at a point of sale. The label also reinforced the strength of the bag in the area of the hole to prevent tearing when the bag is hung.
While such machines are faster than strictly manual application of a label to a bag, in the case of both semiautomatic and automatic machines, if the operator presents the bag to the machine in an out of square condition, the label is applied out of square to the bag, resulting in an unsightly bag. This result often occurs given the fact that an inexact human step is involved in both processes. Because of the repetitive nature of the operation, many prior processes include counter balance devices to reduce operator stress and fatigue, but speeds are still held to a maximum of approximately twenty bags per minute per human operator.
Attempts have been made to completely automate application of a label to a bag emanating from a vertical form, fill and seal machine. The most successful of these attempts has been to apply a label to the front of the bag only (not a saddle label) by tacking a heat seal label to the bag film in the area of the forming tube (before the bag is filled) so that as the forming tube is advanced, the label is stopped in the area of the sealing jaws, where it is heat sealed to the bag, a hole is punched, and the bag is severed just above the label. Such machines were made by Hayssen Manufacturing Company, Sheboygan, Wis., U.S.A. beginning in about the mid 1960's.
Another method of forming a sealed bag is to apply a "simulated header", where the packaging material is actually printed to look like a header, and the sealing system of the vertical form, fill and seal machine is enlarged to seal the complete area of the simulation of the label. In the case of polyethylene, a seal is made at the top of the simulated area and a secondary seal is made at the bottom of the simulated area. However, no label is actually applied to the bag.
No apparatus or method exists to automatically apply a saddle label, made only of paper, to the top of a bag with the label being absolutely square on the top of the bag. The purpose of the present invention is to provide a method and apparatus, automatic from start to finish, for regularly and accurately applying saddle labels to bags in a fully automatic fashion.